The present invention relates to process control systems of the type used to monitor and/or control operation of industrial processes. More specifically, the present invention relates to monitoring data on process control loops used in such systems.
Field devices (devices such as process controllers, monitors and transmitters) are used in the industrial process control industry to remotely control or sense a process variable. For example, a process variable such as temperature, pressure, etc., may be transmitted to a control room by a process variable transmitter. The sensed process variable can be used to control the process or can provide information about process operation to an operator. For example, information related to pressure of a process fluid may be transmitted to the control room and used to control the process, such as by controlling a valve in an oil refinery.
Communication with field devices can be through a number of techniques. One technique is through the use of a process control loop. Such process control loops have two wires which are used for carrying data. In some installations, the two wires are also used to power field devices. One process control loop signaling protocol is a 4-20 mA signal which is used to represent a process variable. Another signaling technique is the HART® communication protocol superimposes digital information on top of the 4-20 mA signal. Another technique is generally referred to as the Fieldbus communication protocol in which the analog current level on the loop is not used for transmitting information and all data is carried digitally.
As the complexity of communication protocols have increased, the complexity of the network configuration of field devices in industrial processes has also increased. In an installation with a complex network topology, it can be particularly difficult to diagnose and identify failures related to the communication network.